“Biochips” or arrays of binding agents, such as oligonucleotides, cDNA and peptides, and the like have become an increasingly important tool in the biotechnology industry and related fields. These binding agent arrays, in which a plurality of binding agents, i.e., ligands or molecules, are deposited onto a solid support surface in the form of an array or pattern, find use in a variety of applications, including gene expression analysis, drug screening, nucleic acid sequencing, mutation analysis, and the like.
In many instances, the solid support surface upon which the binding agents are deposited is a glass substrate. In order to produce these glass substrates, and in particular a plurality of glass substrates, usually a large precursor sheet of glass is scribed and then broken into a plurality of smaller pieces, where the smaller pieces are used as the substrates upon which substances are deposited, as described above. Scribing involves cutting the glass to form a groove therein, where the groove may be formed by removing material from the glass or may be formed by reconfiguring the glass to create a groove. Precursor glass suitable for use with biopolymeric microarrays can be scribed using a variety of means including, but not limited to, mechanical protocols that employ natural diamonds, carbide wheels and lasers.
In using, for example, a diamond to scribe glass, a sharp point of a diamond physically contacts the glass to make a cut therein. However, while the use of diamonds is effective to scribe and singulate glass, it presents numerous problems. First and foremost, the diamond undergoes wear during use, which eventually results in the deterioration of its scribing abilities. For example, ineffective scribe depths may result and/or the scribed edges may decline in quality causing cracks, all of which may result in unusable glass.
To ensure that deteriorated diamonds are not used, it is incumbent upon an operator to constantly inspect the diamonds in attempts to detect the deterioration before it becomes too severe. This manual detection process requires the system to be shut down, resulting in increased costs and time delays. Furthermore, all too often the inspections are inadequate or untimely, ultimately resulting in glass breakage as a result of the ineffectively scribed glass. Additionally, scribing glass with diamonds oftentimes produces microfractures that can propagate perpendicularly outward from the scribe line which weaken the glass. Another significant disadvantage is that diamond scribing also produces glass shards which oftentimes end up on the surface of the glass contaminating it, for example when the glass is used as a substrate for microarrays.
Likewise, for reasons analogous to those described above for diamonds, carbide particles also present numerous problems for scribing glass.
In light of the above described problems associated with the use of diamonds and carbide particles to scribe glass, lasers have become an increasingly popular tool to scribe glass. However, while effective at producing precise and reproducible scribe lines, laser glass scribing oftentimes produces protrusions at the edges of the scribed glass. FIGS. 1 and 2 show a prior art method of scribing glass using a laser and the glass pieces produced thereby. FIG. 1 shows a precursor glass sheet 2. To scribe the glass, a laser enters the sheet at an entrance point 1 to begin the scribe line 4 and exits at the end of the scribe line at an exit point 3. This is repeated for each scribe 4, i.e., for each proposed glass edge, so that a plurality of glass pieces are produced, each having a primary or intended width 70. FIG. 2 shows an individual piece of glass singulated or broken apart from the precursor glass sheet of FIG. 1. As shown in FIG. 2, at the laser beam's entrance and exit from the glass sheet, i.e., at the beginning and ending of the scribe line, laterally extending, substantially planar edge protrusions 100 and 102 (i.e., the protrusions may less than or the same thickness of the glass) are produced due to the laser acting upon the glass. Accordingly, primary width 70 is extended or increased by dimension 72. Such protrusions may vary in dimensions, i.e., may vary in the magnitude of the dimension, depending on the size of the precursor glass, the power of the laser, etc. However, typically a protrusion will increase the primary width, i.e., the intended width, of the scribed glass by as much as about 100 microns to about 350 microns.
These edge protrusions are reproduced at the beginning and ending of each scribed line or edge, causing decreased yields, inconsistent edge quality (which may be a source of cracks) and storage and/or packaging problems due to the irregular and inconsistent shapes. To physically remove such protrusions from the ends of the glass results in time delays and increased costs and may further weaken the glass.
As such, there is continued interest in the development of new methods that employ lasers to scribe glass having straight, smooth edges substantially free of edge protrusions. Of particular interest would be the development of such methods that are easy and inexpensive to use, do not interfere with the surface of the glass precursor sheet and do not produce the above described protrusions.